1. Technical Field of the Invention
This invention relates generally to the field of communications antennas. More specifically the present invention relates to electronically reconfigurable and beam-steered planar antenna structures.
2. Background
The development of antennas for use on moving platforms such as aircraft and ground vehicles has not been particularly difficult for low frequency applications where near-omnidirectional antenna beam patterns provide sufficient radio frequency (RF) gain. However, at higher frequencies an air or ground vehicle antenna must possess a degree of spatial directionality to achieve sufficient gain to close transmit and receive communications links.
Spatially-directional antennas used in air and ground vehicle applications must also have beam steering capabilities in order to maintain line-of-sight communications. Where the dynamics are not too great, beam steering on moving platforms has been accomplished by mechanical steering means. However, when platform dynamics are high, electronic beam phase-shift steering is the only means that will suffice.
When airborne antenna applications will have an adverse impact on aerodynamics, planar, electronically phase-shift steered antennas represent the only viable solution because they afford integration into the airframe with minimal disturbance to airflow. Conformal antennas provide the ultimate solution to integration into an airframe because conformal arrays can be shaped to match portions of an aircraft such as fuselages and even wing leading edges. The application of multiple conformal arrays also relaxes the requirements for phase steering because at any given time the conformal array pointed being oriented nearest to boresight can be selected to carry the communications link.
Moreover, because antennas are generally designed to operate at a given relatively narrow frequency band, by design, their operational frequency range is generally fixed. Wide bandwidth antennas solve the problem of having to integrate a separate system of antenna arrays into an aircraft for each frequency band of interest. To the extent that a single antenna array can be reconfigured in real time to support multiple frequency bands of operation, the better in terms of power, weight, and space.
What is needed therefore is a communications antenna system and structure that provides real time control over electronic beam steering and operational frequency band, while possessing a simple planar structure with adaptability to conformal integration with a host platform.